ATC-Weather
Atmospheric Pressure - answer A measure of weight that a column of air exerts on an
object
Pressure Variation - answer Standard atmospheric values are used as standard
scientific measurements
-At Sea level
-Surface Temperature 15 C/59 F
-Surface Pressure 29.92 inches of mercury/1013.2 millibars
-Weight of atmosphere at sea level 14.7lbs PSI
-All standards (temperature, dew point, pressure) vary because of altitude.
-Pressure decreases roughly 1 in of Mercury every 1,000 ft increase in altitude
Types of Barometers - answer Mercurial Barometer
Aneroid Barometer-partially evacuated cell expands and contracts with changes in
atmospheric pressure
Altimeter Setting Indicator - answer ASI-very accurate
-Precision aneroid barometer
-Primary means of obtaining altimeter settings at terminal facilities, which is the station
pressure.
-Station Pressure with a correction factor for field elevation above or below sea level is
Altimeter Setting.
Altimeter - answerForm of aneroid barometer, which is graduated to read increments of
height rather than units of pressure.
Controller gives altimeter setting for ASI to pilot, pilot inputs altimeter setting into aircraft
altimeter and indicates altitude above mean sea level.
Altitude - answerThe height measured in feet Above Ground Level (AGL), or from Mean
Sea Level (MSL)
True Altitude - answerAn actual or exact altitude above mean sea level. Given by ATC
Indicated altitude - answerAn altitude above MSL indicated on altimeter. Given by
instrument
Altimeter Setting - answerThe value to which the scale of the pressure altimeter is set
so the altimeter indicates true altitude at field elevation
,Effect of pressure on altitude - answer-Failure to adjust the altimeter as the aircraft files
from a high-pressure area to a low-pressure area; the aircraft is lower than aircraft
altimeter indicates. (High to low, look out below. Lower than actual)
-Altimeter must be adjusted frequently to the altimeter setting reported by the nearest
tower or weather station.
-Aircraft flies from low pressure to high pressure, the aircraft is actually higher than the
altimeter indicates. (low to high, eye to sky; higher than actual)
-A pressure change of one-inch mercury would result in a 1,000 -foot error on the
altimeter.
Effects of temperature on altitude - answer-Temperature varies with altitude. Normally
temperature decreases with an increase in altitude
-Standard lapse rate is 2 C or 3.3 F per thousand feet.
-Aircraft flying from warm to cold air, the aircraft will be lower than altimeter indicates.
-Aircraft flying from cold to warm air the aircraft will be higher than the altimeter
indicates.
Pressure Altitude - answer-The altitude in the standard atmosphere where the current
pressure surrounding the aircraft is found.
-Pilot sets altimeter at the standard altimeter setting of 29.92 inches; the altimeter
indicates pressure altitude
-FAA regulations require aircraft to fly at pressure altitudes at high levels (18,000 feet
and above)
-Below 18,000 feet, aircraft are required to fly at indicated altitudes
Density Altitude - answer-The altitude in the standard atmosphere where density of the
air surrounding the aircraft is found
-Pressure, temperature, and humidity determine air density
-an index to aircraft performance
High density Altitude - answer-Hot day, the air becomes thinner or lighter, and its
density is equivalent to a higher altitude in the standard atmosphere.
-Reduces aircraft performance by reducing power, thrust, and lift.
-Lengthens takeoff and landing rolls.
-Reduces the rate of climb
Low Density altitude - answerIncreases aircraft performance.
Wind and Atmospheric Circulation - answerConvection & Advection
Convection - answer-Two surfaces heated unequally cause the uneven heating of the
air above. Warm air expands and becomes lighter than the cooler air.
-The warm air expands and becomes lighter than the cooler air
-The cooler air is drawn to the ground, which forces the warm air to rise
-As the warm air rises, it begins to cool, eventually descending to start the cycle over
again.
, -The horizontal air flow in a convective current is wind
Advection - answerHorizontal movement of wind; can transfer heat or atmospheric
properties from one area to another
Circulation - answerCoriolis Force, Circulation, Jet Streams, Isobars, Low pressure
area, High pressure area
Coriolis Force (Effect) - answer-Action caused by the rotation of the earth
-Affects the paths of air currents.
-Defects air to the right in the Northern Hemisphere
-Deflects air to the left in the Southern Hemisphere
Circulation - answer-Air flowing from areas of higher pressure to areas of lower
pressure. Hi to low
-Atmospheric circulation is a convective current occurring on a large scale
-Warm air heated at the equator expands and becomes lighter
-Cold air flows from the poles toward the equator forcing the warm air up which then
flows toward the poles
Jet Steams - answer-A narrow band of strong winds moving through the upper
atmosphere
-High level boundaries separating warm/cold air ie. tropical air from polar air.
-Associated with frontal movements
-Lower in altitude in winter and further south towards the equator
-Higher in altitude in summer and further north towards the poles
-Creates high level windshear/clear air turbulence (CAT)
-No clouds due to cold dry air in jet stream
Isobars Additional circulation problems - answer-Irregular distribution of oceans and
continents
-Daily variation in temperature
-Isobars: Lines drawn on weather maps to connect points of equal pressure, used to
plot and identify organized pressure points at sea level
Low Pressure Area - answer-Region of the atmosphere where the pressure decreases
toward the center
-Wind flow around the system is counterclockwise (cyclonic) in the northern hemisphere
-Unfavorable flying conditions in the form of
-low clouds, restricted visibility due to precipitation, strong gusty winds, and turbulence.
High Pressure Area - answer-A region of the atmosphere where pressure increases
toward the center
-WInd flow is clockwise (anticyclonic) in the northern hemisphere.
-Flying conditions generally move favorable because of
Atmospheric Pressure - answer A measure of weight that a column of air exerts on an
object
Pressure Variation - answer Standard atmospheric values are used as standard
scientific measurements
-At Sea level
-Surface Temperature 15 C/59 F
-Surface Pressure 29.92 inches of mercury/1013.2 millibars
-Weight of atmosphere at sea level 14.7lbs PSI
-All standards (temperature, dew point, pressure) vary because of altitude.
-Pressure decreases roughly 1 in of Mercury every 1,000 ft increase in altitude
Types of Barometers - answer Mercurial Barometer
Aneroid Barometer-partially evacuated cell expands and contracts with changes in
atmospheric pressure
Altimeter Setting Indicator - answer ASI-very accurate
-Precision aneroid barometer
-Primary means of obtaining altimeter settings at terminal facilities, which is the station
pressure.
-Station Pressure with a correction factor for field elevation above or below sea level is
Altimeter Setting.
Altimeter - answerForm of aneroid barometer, which is graduated to read increments of
height rather than units of pressure.
Controller gives altimeter setting for ASI to pilot, pilot inputs altimeter setting into aircraft
altimeter and indicates altitude above mean sea level.
Altitude - answerThe height measured in feet Above Ground Level (AGL), or from Mean
Sea Level (MSL)
True Altitude - answerAn actual or exact altitude above mean sea level. Given by ATC
Indicated altitude - answerAn altitude above MSL indicated on altimeter. Given by
instrument
Altimeter Setting - answerThe value to which the scale of the pressure altimeter is set
so the altimeter indicates true altitude at field elevation
,Effect of pressure on altitude - answer-Failure to adjust the altimeter as the aircraft files
from a high-pressure area to a low-pressure area; the aircraft is lower than aircraft
altimeter indicates. (High to low, look out below. Lower than actual)
-Altimeter must be adjusted frequently to the altimeter setting reported by the nearest
tower or weather station.
-Aircraft flies from low pressure to high pressure, the aircraft is actually higher than the
altimeter indicates. (low to high, eye to sky; higher than actual)
-A pressure change of one-inch mercury would result in a 1,000 -foot error on the
altimeter.
Effects of temperature on altitude - answer-Temperature varies with altitude. Normally
temperature decreases with an increase in altitude
-Standard lapse rate is 2 C or 3.3 F per thousand feet.
-Aircraft flying from warm to cold air, the aircraft will be lower than altimeter indicates.
-Aircraft flying from cold to warm air the aircraft will be higher than the altimeter
indicates.
Pressure Altitude - answer-The altitude in the standard atmosphere where the current
pressure surrounding the aircraft is found.
-Pilot sets altimeter at the standard altimeter setting of 29.92 inches; the altimeter
indicates pressure altitude
-FAA regulations require aircraft to fly at pressure altitudes at high levels (18,000 feet
and above)
-Below 18,000 feet, aircraft are required to fly at indicated altitudes
Density Altitude - answer-The altitude in the standard atmosphere where density of the
air surrounding the aircraft is found
-Pressure, temperature, and humidity determine air density
-an index to aircraft performance
High density Altitude - answer-Hot day, the air becomes thinner or lighter, and its
density is equivalent to a higher altitude in the standard atmosphere.
-Reduces aircraft performance by reducing power, thrust, and lift.
-Lengthens takeoff and landing rolls.
-Reduces the rate of climb
Low Density altitude - answerIncreases aircraft performance.
Wind and Atmospheric Circulation - answerConvection & Advection
Convection - answer-Two surfaces heated unequally cause the uneven heating of the
air above. Warm air expands and becomes lighter than the cooler air.
-The warm air expands and becomes lighter than the cooler air
-The cooler air is drawn to the ground, which forces the warm air to rise
-As the warm air rises, it begins to cool, eventually descending to start the cycle over
again.
, -The horizontal air flow in a convective current is wind
Advection - answerHorizontal movement of wind; can transfer heat or atmospheric
properties from one area to another
Circulation - answerCoriolis Force, Circulation, Jet Streams, Isobars, Low pressure
area, High pressure area
Coriolis Force (Effect) - answer-Action caused by the rotation of the earth
-Affects the paths of air currents.
-Defects air to the right in the Northern Hemisphere
-Deflects air to the left in the Southern Hemisphere
Circulation - answer-Air flowing from areas of higher pressure to areas of lower
pressure. Hi to low
-Atmospheric circulation is a convective current occurring on a large scale
-Warm air heated at the equator expands and becomes lighter
-Cold air flows from the poles toward the equator forcing the warm air up which then
flows toward the poles
Jet Steams - answer-A narrow band of strong winds moving through the upper
atmosphere
-High level boundaries separating warm/cold air ie. tropical air from polar air.
-Associated with frontal movements
-Lower in altitude in winter and further south towards the equator
-Higher in altitude in summer and further north towards the poles
-Creates high level windshear/clear air turbulence (CAT)
-No clouds due to cold dry air in jet stream
Isobars Additional circulation problems - answer-Irregular distribution of oceans and
continents
-Daily variation in temperature
-Isobars: Lines drawn on weather maps to connect points of equal pressure, used to
plot and identify organized pressure points at sea level
Low Pressure Area - answer-Region of the atmosphere where the pressure decreases
toward the center
-Wind flow around the system is counterclockwise (cyclonic) in the northern hemisphere
-Unfavorable flying conditions in the form of
-low clouds, restricted visibility due to precipitation, strong gusty winds, and turbulence.
High Pressure Area - answer-A region of the atmosphere where pressure increases
toward the center
-WInd flow is clockwise (anticyclonic) in the northern hemisphere.
-Flying conditions generally move favorable because of
